Removing criteria line on sample plots

Removed criteria line on sample plots for all except NO23 plots
Fix legend handling for null
Merge pull request #227 from isuftin/NAWQAAN-307

Fix legend handling for null
Merge pull request #224 from mbucknell/NAWQAAN-304

Nawqaan 304
Refactored TimeSeries object

- No longer a global configuration for 1993
- Moved cut-off functionality into a self-contained function with an
incoming param switch (default to true) whether or not to cut off date
to lower bound (1993 currently)
Merge pull request #228 from isuftin/NAWQAAN-315

Refactored TimeSeries object
Merge pull request #225 from isuftin/NAWQAA-316

Removing criteria line on sample plots
Changed wording for N criteria line
Merge pull request #229 from isuftin/master

Changed wording for N criteria line
Removed the popup help for Human-Health benchmarks and replace with a
link to the Technical Information page. Added hover tooltip to benchmark
graph per JIRA.